Can Dogs Smell Our Feelings?

We’ve all probably heard it in a movie before: “Dogs can smell fear.” But have you ever wondered how that actually works? 

There’s no doubt that our pups’ noses are extraordinarily powerful. For confirmation, just think about the last time you opened a bag of chips from across the house and they came running or how even a short walk down the block inevitably turns into a “sniffari” with stops every few feet. Dogs can sniff out cancer and diabetes, and even the zits on our faces. So, it’s no surprise that they can also detect certain human emotions simply based on the odors we excrete. 

Dr. Zoe Parr-Cortes is a veterinarian and PhD graduate from the University of Bristol whose research team conducted a groundbreaking study on the subject of how human emotions affect our dogs. She points out that dogs’ intuition for human emotions likely serves a specific purpose.

“As one of our closest companions, dogs have co-evolved alongside humans for thousands of years,” Dr. Parr-Cortes says. “Detecting stress or fear response in others within a social group, sometimes called ‘emotional contagion,’ is thought to be beneficial, especially if it signals a possible threat in the environment.”

As for how our dogs’ sniffers affects our relationships with them? Read on to find out.

How do dogs smell our emotions?

You know how when you’re under pressure, your armpits tend to smell worse than usual? (No? Just me? Great.) That’s because stress-sweat is a chemically different kind of sweat. And if we can tell that from just a whiff, you bet our dogs can, too. 

Dogs can register the minute nuances of all sorts of human body odors. For example, they can detect diabetes based solely on how our breath smells. As for the whole “dogs can smell fear” thing, Dr. Parr-Cortes confirms that there is, indeed, evidence that dogs can be trained to smell the difference between sweat samples collected from stressed and non-stressed humans. 

“While we don’t know what exactly dogs are smelling, we know that dogs can be trained to detect changes in cortisol in humans,” Dr. Parr-Cortes says. “For example, dogs trained on scent by medical detection dogs in the U.K. can alert people with Addison’s disease when their cortisol levels drop too low.”

Do dogs smell some emotions better than others?

OK, so our dogs can tell when we’re nervous. But what about all of the other human emotions, like joy, anger, and ennui? Could an ambitious human with a particular distaste for their therapist’s office train a dog to tell us what they’re feeling, when they’re feeling it?  

Maybe! Well, kind of. “There are several studies that show that dogs respond to the smell of different emotions including fear, happiness, and sadness, with measurable changes in heart rate and behavior,” Dr. Parr-Cortes says. (Still, though, please don’t fire your therapist. As someone who often complains about everyday trivialities to my disinterested hound, I can confirm that our dogs are not equipped to teach us coping skills.)

We don’t yet know if there are any emotions our dogs can’t smell, Dr. Parr-Cortes adds, because we haven’t tested them all. Even if we had, it could also be hard to prove our dogs can’t smell something. After all, Dr. Parr-Cortes says, “Even if we don’t see a response we can measure or an obvious change in behavior, it doesn’t mean dogs can’t smell it. It just means we don’t have evidence of an effect, either because the smell doesn’t change behavior or because any change was too subtle for our measures to detect.”

That said, if you’re wondering about that TikTok trend saying dogs can smell that we love them, it seems that theory, at least, is bunk.

How do our emotions affect our dogs?

Dr. Parr-Cortes has actually researched that exact question. Specifically, she and a research group from the University of Bristol conducted a study that examined how the presence of human stress hormones affected dogs’ decision-making. The study was the first to show how the scent of human emotions — specifically, stress and relaxation — can affect dogs’ emotional state. 

The 2024 study began by training 18 canine participants that one bowl on one side of the study room always contained food, while the other bowl on the opposite end was always empty. Naturally, the dogs began to favor the bowl that always rewarded them, approaching it more quickly. Then, the researchers created an ambiguous situation by removing the two bowls and replacing them with a third in the middle of where they’d been. Dr. Parr-Cortes and her team wanted to see if the dogs would be optimistic about the third bowl and rush to it, or if they’d be more pessimistic and approach slowly.

Here’s where humans’ emotions came in: The researchers also put human volunteers through a stress test before giving them 20 minutes to relax with videos of forest and seaside scenes. During both activities, the researchers measured stress indicators like cortisol levels, heart rate, heart rate variability (HRV), and self-reported anxiety. They also collected breath and sweat samples. Before releasing the dogs to investigate the new bowls, the pups’ handlers had them sniff the human-odor samples, repeating the process several times with the bowls in all three positions and the stressed/relaxed smells in varying orders.

The result? The researchers found that the dogs were more hesitant to approach the ambiguously located bowls after they’d smelled the samples with the stress smells. The samples without stress smells had no effect.

“Our findings suggest that the smell of stress may have reduced how willing the dogs were to take a ‘risk’ in a situation where a positive outcome seemed unlikely,” Dr. Parr-Cortes says. “This could be a way for the dog to avoid disappointment and conserve energy.”

Dr. Parr-Cortes also notes that the dogs used in the study were untrained, and the samples used came from people they didn’t know. “This suggests that there may be a common ‘stress’ scent in humans that dogs can identify without prior training,” Dr. Parr-Cortes says. “So, from this study, we know that odor is important, but in everyday life, it’s likely many other cues, like body language, sounds, and sights are also important.”

Can we use emotions to improve our dogs’ training and wellbeing?

The 2024 study’s findings provide fascinating insights into how our own moods can affect our dogs’ emotional states. That can also offer some clues as to how we can create more harmony with them during training — though for the most part, the researchers’ findings seem to confirm ideas that have already become popular among many trainers.

Because the dogs became more hesitant around stress smells but displayed no measurable response to the non-stress smells, Dr. Parr-Cortes suggests that “keeping calm or even doing a relaxing activity before training” could improve training outcomes.

“We know from lots of studies that using positive training with lots of rewards is good for your relationship with your dog, but this suggests that being around you when you’re stressed or arguing might have a negative effect on your dog’s mood and maybe even your relationship with your dog and its response to training,” Dr. Parr-Cortes says. “So, keeping your relationship with your dog happy and based on positive reinforcement and fun engagement is the best way to have a good relationship and a happy dog.”

What do we have left to learn?

Although Dr. Parr-Cortes and her team’s study was the first of its kind, she believes it also opens doors to even more questions.

“When interpreting our emotions in real-life scenarios, dogs likely use a combination of cues, such as our body language, voice tone, and, as we’ve found, odor, so it would be interesting to examine the relative importance of each cue,” Dr. Parr-Cortes says. “Especially since smell is so important to dogs.”

In the future, the researchers hope to examine how other emotions, like happiness and deep relaxation, affect dogs’ cognitive bias and mood. “It would also be interesting to look at the effect of repeated exposure to odors of stress and other emotions,” Dr. Parr-Cortes says, “rather than just a one-off test.”

For now, it’s at least nice to know our pups can at tell when we’re feeling the crunch and need a little TLC. Maybe that’s why they make such good cuddle buddies.